Interlocking mechanism



June 2, 1959 R. E. BOYNIN ET AL 2,889,420

INTERLOCKING MECHANISM Filed June 17, 1957 3 Sheets-Sheet 1 1 4 4 V IF:7 a3 1: 36 a 29 I Inventors:

Richard E.BOT1iT'I, George R.Townsend,

b5 T air A torney.

June 2, 1959 Filed June 17, 195'? 7'0 ISOLA Tl/VG SW/TCH T0 MOTORSTART/N6 SWITCH R. E. BONlN ET AL INTERLOCKING MECHANISM 3 Sheets-Sheet2 I I z Inventors:

Richard E. Benin, George R. Townsen cl,

heir Attorneg.

June 2, 1959 R. E. BON lN ET AL 2,889,420

INTERLOCKING MECHANISM Filed June 17, 1957 5 Sheets-Sheet 3 Inventors:

Richard E. Benin,

George R. Townsend,

bg w

- T eh- A tonneg.

United States Patent INTERLOCKING MECHANISM Richard E. Bonin and GeorgeR. Townsend, Roanoke, Va., assignors to General Electric Company, acorperation of New York Application June 17, 1957, Serial No. 666,071 17Claims. (Cl. ZOO-50) This invention relates to interlocking mechanismfor circuit control equipment, more particularly to interlock ingmechanism for circuit control equipment of the enclosed type havingcircuit control switches and separate access doors therefore, and it hasfor an object the provision of a simple, reliable and improvedinterlocking mechanism of this character. Such control equipment mayinclude high voltage current limiting fuses, high voltage line isolatingswitches, and contactors of the electromagnetically operated type and.their associated control devices mounted in suitable metal cabinets orcompartments that may be assembled to meet widely varying circuitcontrol requirements and provided with separate access doors. Althoughnot limited thereto, such variously assembled enclosed equipment isparticularly useful in high voltage heavy duty industrial motor controlapplications. i

In conventional methods of mechanical interlocking in which it isdesired to have the movement of one member from an inital positiondepend upon the position of another member or members, it is customaryto insert an interlocking linkage in such a manner that if movement ofthe first member is initiated when the second member is in a positionwhich requires the first member to be retained in its initial position,the first member will be restrained from moving by means of aninterlocking linkage bearing directly on some portion of the secondmember. Interlocking mechanism of this character operates satisfactorilyin equipments in which the interlocking linkage is relatively short inlength and in which the second member can withstand any force whichcould be applied to it by the first member. However, in equipments inwhich a relatively long interlocking linkage is used the interlockingmechanism becomes unstable when relatively large forces are transmittedthrough the linkage to the second member. In such equipments and inequipments in which for any reason it is undesirable to subject thesecond member to stresses of the magnitude that it would be possible totransmit to it as a result of force applied to the first member, aconventional interlocking mechanism is unsatisfactory and leavesomething to be desired. Accordingly, a further object of this invention is the provision of an interlocking mechanism having means forlimiting to a predetermined value the magnitude of the force that can betransmitted from the first member to the second member.

In carrying the invention into etfect in one form thereof, an operatingmember and a movable second member are provided together with a linkagemember between them which is driven by the operating member. The secondmember has blocking and non-blocking positions with respect to thedriven linkage member. A yielding driving connection is provided betweenthe operating member and the driven member together with interferencemeans for limiting to a predetermined value the force that can beapplied by the operating member to the driven member to be transmittedto the second member in its blocking position.

In illustrating the invention in one form thereof, it is shown asembodied in motor control equipment enclosed within a metal cabinethaving separate access doors for the isolating switch, meters andinstruments, and electro-. magnetically operated contractor. Theinvention itself both as to the elements and their organization togetherwith. further objects and advantages will best be understood byreferring to the following description taken in connection with theaccompanying drawings of which Fig. l is a view in front elevation of atypical multiple. tier cabinet assembly for enclosing high voltagethree.- phase motor control equipment to which the improved interlockingmechanism of the invention may appropriately be applied shown withseveral of the compartment doors open to reveal the motor circuitcontrol switches therein. Fig. 2 is a fragmentary view in side elevationof the lower portion of the assembly shown in Fig. l with portions ofthe cabinet wall broken away more clearly to reveal the common doorlatching mechanism. Fig. 3 is a view in perspective of a preferred formof; the

interlocking mechanism of the invention shown as applied;

to the interlocking of two switches one located in the top compartmentand the other in the bottom. compartment of the cabinet of Fig. 1. Fig.4 is a plan view of a detail of the mechanism illustrated in Fig. 3.view of a portion of the interlock mechanism of Fig. 3 illustrating therelative positions of parts of the interlocking mechanism during anoperating condition in which the second member is. in a position whichrequires that the operating member be prevented from moving from apredetermined initial position. Fig. 6 is a view in front elevationofthe upper portion of the mechanism of Fig. 5 showing the relative.positions of the parts during another operating condition in which theposition of the second member is such that the operating member maybepermitted to move from such initial position. Fig. 7 is a view inperspective of a modified form of the interlocking mechanism of Figs. 1to 6 inclusive, Fig. 8: is a front view of the modified form of Fig. 7illustrating the relative positions of parts during an operating con-.dition in which the second member which is to be interlocked with theoperating member is in a position which requires the operating member tobe prevented from moving from a predetermined initial position, and Pig.9 is a front view of the mechanism of Figs. 7 and 8 illustrating therelative positions of the parts during an operating condition in whichthe second member is in a position in which movement of the operatingmemberfrom such initial position is permissible.

Referring now to the drawings and particularly to Fig. 1, in an uppercompartment C1 of the enclosing cabinet 1 are mounted the current limitshort circuit protective fuses 2 and a three-phase gang disconnectswitch 3. for isolating from the power supply lines 4 the fuses, mainstarting contactor and associated metering and control devices. Thearrangement is such as to permit removal and replacement of a blown fuseonly when the isolating switch 3 and the access door DCl are open asshown. This switch is provided with an operating member which isillustrated as a shaft 5. As shown in Figs. 3, 5 and 6, this shaft 5extends from the rear wall of the compartment C1 to the access door D01and is journaled for rotation in a bearing bracket 5a which is securedto the wall of the cabinet 1 by any suitable means such for example aswelding. In the end of shaft 5 nearest the compartment access door DCIis mounted a pin 6. The door-latching and unlatching handle 7 carries ayoke 8 which may be moved into engagement with the pin 6 for closingisolating switch 3 only when the access door is closed. Upon movement ofthe handle to its down position, the latching dog 9 passes behind thelip 1a of the front cabinet wall and latches the door DC1 closed.

Fig. 5 is a front An interlocking linkage rod 10 extends between theoperating shaft 5 in the upper compartment C1 and the interferencemember of a motor-starting switch in the lower compartment C2. Thislinkage rod is mounted for vertical lengthwise sliding movement in guidebrackets 10a and 10b secured to the side wall of the enclosing cabinet.Operation of the handle 7 to its isolating switchclosing anddoor-latching position raises the interlocking linkage member 10 to movethe latch 11 into latching position with the latching bracket 12 carriedon the inside of the lower compartment access door DC2. In this manneraccess to the three-phase high voltage motorstarting switch or contactor14, which is mounted in the lower compartment C2 and connected in serieswith the isolating switch 3, is prevented when the isolating switch isclosed.

The three-phase motor-starting switch 13 is normally open and iselectromagnetically operated to the closed position by means of asuitable electromagnet 14 (see Fig. 2) which may be energized anddeenergized by means of suitable manually operated switches, preferablyof the pushbutton type, or by automatic control not shown. Whenenergized, the electromagnet 14 rotates the shaft 15 to close suitablethree-phase switch contacts which, in accordance with standard practice,may be provided with magnetic blowouts and removable arc chutes 16.Ordinarily, overload protection for the motor circuit is provided sothat the electromagnet 14 may be automatically deenergized by means of asuitable overload responsive relay not shown. In any event, reverserotation of shaft 15 will open switch 13 whenever the operatingelectromagnet 14 is deenergized.

As the motor-starting switch 14 is closed and opened a bell crank arm17, extending from the operating shaft 15, moves a link 18 to effectrotation of a motionamplifying bell crank arm 19 (see Fig. 3) about itspivot pin 20. This pin is mounted on a bracket 21 which extends from theframe of the three-phase motor-starting switch as shown in Fig. 3. Themotor switch 13 is provided with an interference member which isillustrated as a bar 22 pivotally connected by means of a pin 23 to thelong arm of the motion-amplifying bell crank 19 and through the bellcrank to the movable contactcarrying member of the switch. It is mountedto slide in suitable guide blocks 24 and 25 into and out of blockingrelationship with the lower end of the interlocking linkage member 10.Thus whenever the motor-starting switch 13 is closed, interferencemember 22 will slide under the lower end of linkage member 10 to lockthe latch 11 in latching relationship with the door latch bracket 12 andalso to lock handle 7 in its down position thereby to prevent opening ofthe isolating switch 3 as long as the motor-starting switch remainsclosed. At the same time both access doors DC1 and DC2 are lockedclosed.

In many equipments and installations in which two members are to beinterlocked, the distance between them is such as to require arelatively long interlock link. For example in apparatus of thecharacter disclosed in Figs. 1, 2 and 3 the distance between theisolating switch operating member 5 and the interference member 22 ofthe motor switch 13 may be 72 inches or more thus requiring theinterlock link 10 to be of approximately the same length. For thepurpose of eliminating from the interlocking mechanism instabilityproduced by such relatively long interlocking link and also for thepurpose of limiting to a low value the force that can be transmitted bythe interlock link 10 to the interference member 22, means are providedfor limiting the force that can be applied by the operating member 5 todrive the driven interlock member 10. These means comprise a yieldingdriving connection between the operating member and the driven member 10and means for blocking the movement of the operating member if thedriven member 10 does not move a predetermined distance from an initialposition in response to a predetermined amount of movement of theoperating member from a corresponding initial position. Illustrated ascomprising the yielding driving connection and blocking means are an arm26 keyed to the shaft arm and provided with pins 27 and 28, a bracket 29secured to the link member 10 and provided with a pin 30 together with aresilient member such as the coil spring 31 connected between the pins28 and 30 and stressed to bias the bracket 29 into engagement with pin28. The free end of the bracket 29 is returned at right angles toprovide an interference surface in the path of pin 27. For actuating theisolating switch in response to rotation of the operating shaft 5, atoggle mechanism comprising toggle arms 32 and 33 is connected betweenthe shaft and the movable contact-carrying member of the switch.

When the isolating switch is closed, the operating shaft 5, arm 26 andtoggle arms 32 and 33 are in the positions in which they are illustratedin Fig. 3. The pins 27 and 28 are located on radii from the center ofthe shaft which are separated by a substantial angle. It will be notedthat in response to rotation of shaft 5 any point on the upper portionof arm 26 such as the square pin 27 will have an initial horizontalmovement and that any point well to the right of center, such as pin 28,will have an initial movement in a substantially vertical direction. Theinitial movement of the junction point of the toggle members 32 and 33is generally substantially vertical. Consequently there is a substantialrotation of operating shaft 5 before there is any appreciable openingmovement of the isolating switch 3. This free movement of the shaftdetermines the distance between the square pin 27 and the interferingend surface of bracket 29. Successful operation has been obtained with adistance between pin 27 and interfering surface 29a equivalent to l8degrees of shaft rotation.

For the purpose of preventing closing of the isolating switch with thelower compartment door DC2 open, means are provided for blocking theupward movement of the interlock member 10 until the door is closed.This means is illustrated as a spring biased interference bracket 34mounted for lengthwise sliding reciprocating movement in a U-shapedbracket 35 which is secured to the guide bracket 10b in a position suchthat the face of its up-turned end 34a engages the opposing face of thedoor latch 12 when the door is closed. With the linkage rod 10 in itslower position and the door open, the spring 34b moves the bracket 34over and past the bentover end of the latch member 11 as illustrated inFig. 4 to block upward movement of the linkage rod.

With the foregoing understanding of the elements and their organization,the operation of the interlocking mechanism will readily be understoodfrom the following detailed description. Assuming the isolating switch3, the motor switch 13 and access doors DC1 and DC2 to be closed, theelements of the interlocking mechanism occupy the positions in whichthey are illustrated in Fig. 3. The isolating switch is not constructedfor current interruption. Consequently the motor switch 13 must beopened prior to opening the isolating switch and similarly the isolatingswitch must be closed prior to closing the motor switch. As previouslypointed out, opening and closing of the motor switch may be accomplishedeither by automatic or manual control. Opening of the motor switchwithdraws its interference member 22 from blocking relationship with thelower end of interlock linkage rod 10. The door handle 7 of compartmentC1 may then be rotated in a clockwise direction. Since pin 28 is securedto arm 26 and bracket 29 is biased against the pin by spring 31, andsince interference member 22 is clear of the path of interlock linkagerod 10, the latter moves downward carrying with it bracket 29 to permitthe square pin 27 to pass over the top edge of the returned end 29a ofthe bracket Without striking its interfering surface, as illustrated inFig. 6. Consequently, the

clockwise rotation of the operating shaft may be continuedto open theisolating switch to disconnect and thus to isolate the accessible highvoltage components from the line. Continued rotation of the handle 7 andshaft 5 rotates the movable contacts of the isolating switch intoengagement with grounding clips 36 to ground the equipment. The rotationof door handle 7, required to open the isolating switch, turns the latch9 out of latching engagement with the cabinet lip 1a thus permitting thedoor DC l to be opened.

The downwardmovement of interlock linkage rod 10 lowers the top edge oflatching bracket 11 beneath the lower edge of the door latch member 12as shown in Fig. 4 and thus permits the lower access, door DC2 to beopened. In opening, the door withdraws latch member 12 from engagementwith the face 34a of bracket 34 thereby to permit the biasing spring 34bto move the bracket over the top edge of the returned end of the latchbracket 11. This prevents upward movement of rodlt) and thus preventsclosing the isolating switch 3 as long as the bottom access door DC2 isopened.

If the motor switch 13 had not been opened, its interference arm 22would be in blocking position with respect to linkage rod 10 as shown inFig. 3. Consequently, the bracket 29 wouldhave remained in theinterfering position illustrated in Figs. 3 and 5 with its interfering.

surface squarely in the path of the pin 27 on the driving arm 26 Afterl8 degrees rotation of the operating shaft 5, an amount which isinsufficient to open the isolating switch, the pin 27 would engage theinterference surface of bracket 29 and further rotation of the shaftwould be blocked. During this predetermined limited amount of rotationofshaft 5, the biasing stress of spring 31 would be increasedtoacorresponding predetermined relatively low value. Any further increasein force applied to rotate the operating shaft after the pin engagesbracket 29 is absorbed in the guide 1001, which supports the linkage rod10, andv such increased force has no downward component. Consequently,no force in excess of that transmitted by spring 31 is transmitted tothe interference arm 22 of the motor switch. Thus the force that can beappliedto interference arm 22 is definitely limited to a relatively lowvalue and instability of the interlocking mechanism which mightresultfrom application of large forces to drive the relatively long linkagerod It) is eliminated.

In restoring the equipment to service, the doors DCl and DC2 are firstclosed. In the closed position of the door DC2 the door latch memberforces the bracket 34 back over the top edge ofthe latching member 12.The door handle 7 may now be rotated in a counterclockwise direction toclose the isolating switch and latch the door DCI. As a result of suchcounterclockwise rotation of the operating shaft 5, linkage rod 10 israised to elevate the latching member 11 into latching relationship withdoor latch member 12 and simultaneously to lift the lower end of thelinkage rod 10 out of the path of the interfering member of motor switch13 which now may be closed.

In the modification which is illustrated in Figs. 7, 8 and 9, two shaftarms are employed, the arm '26 and a second arm 37. The arm 26 is keyedto the operating shaft 5 with its centerline a predetermined angle, eg18 degrees above the horizontal. Arm 37 is free to rotate on the shaft5, but rests on pin 38 of arm 26 and is biased into engagement with itby means of a torsion spring 39. Pivotally mounted on the supportingbearing bracket 5a is a reaction block 40. In the position in which itis illustrated in Fig. 7 the reaction block 40 is directly in the pathof rotation of the arm 26. However, vertical interlock linkage rod 10 isprovided with an arm 1%! which, if the rod moves downward, rotates thereaction block 40 out of the path of the driving arm 26. The arm 37 islinked by means of a pin and slot connection to the bracket 29 on thevertical rod 10.

If the motor switch 13 is open, its interfering arm 22 does not restrictthe downward movement of the'vertical rod 10. Consequently if the shaft5 is now rotated, the vertical rod 10, bracket 29 and arm 10d descend.The downward movement of arm 10d rotates the reaction block 40 out ofthe path of arm 26 before the shaft has rotated 18 degrees asillustrated in Fig. 9. Consequently the clockwise rotation of theoperating shaft 5 may be continued to open theisolating switch and tounlatch the upper and lower compartment doors. D61 and DC2. On the otherhand, if the motor switch 13 is closed when the switch shaft is rotatedin a clockwise direction, the motor switch interfering arm 22 restrictsthe downward movement of rod 10, bracket 29 and'arm 10d. As a result,the reaction block 40 is not rotated from the position in which it isillustrated, and it will therefore be struck by driving arm 26 when thelatter has rotated 18 degrees from its initial position as illustratedin Fig. 8. Any increase in the applied force beyond that which istransmitted through the torsion spring 39 to the vertical rod at theinstant of engagement of the driving arm 26 with the reaction block 40is absorbed by the latter and is not transmitted through the rod 10 tothe interference arm 22 of the motor switch.

The interlocking mechanism of the invention could be applied in anyapparatus or equipment in which a shaft must be prevented from rotatingbeyond a predetermined number of degrees or a membermust be preventedfrom moving when the position of some remote device or devices makesfurther rotation hazardous to life or equipmerit.

Although in accordance with the provisions of the patent statutes, thisinvention has been described as embodied in concrete form, and itsprinciple of operation has been explained together with the best mode inwhich it is now contemplated carrying that principle into effect, itwill be understood that the apparatus shown and described is merelyillustrative and that the invention is not limited thereto sincealterations and modifications will readily suggest themselves to personsskilled in the art without departing from the true spirit oftheinvention or from the scope of the annexed claims.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. An interlocking mechanism comprising a movable operating member, adriven member, a yieldable driving connection between said members, amovable member having blocking and non-blocking positions with respectto the movement of said driven member, and interference means responsiveto relative movement of said operating member and said driven member forlimiting to a predetermined value the force transmitted by said drivenmember from said operating member to said movable member in its blockingposition.

2. An interlocking mechanism comprising an operating member movablebetween first and second operating po sitions, a driven member, ayieldable driving connection between said members, a movable memberhaving blocking and non-blocking positions with respect to the movementof said driven member, and interference means for limiting to apredetermined value the force transmitted through said yieldableconnection to said driven member comprising means mounted in position toblock said operating member at an intermediate point in its movementbetween said operating positions and removable therefrom in response toa predetermined amount of movement of saiddriven member from an initialposition prior to arrival of said operating member at said intermediatepoint.

3. An interlocking mechanism comprising an operating member, a drivenmember, a yieldable driving connection between said members, a movablemember having blocking and non-blocking positions with respect to themovement of said driven member, and interference means comprising aprojection on said operating member having an initial direction ofmovement angularly disposed with respect to the direction of movement ofsaid driven member and a blocking member disposed in the path of saidprojection and removable from said path in response to a predeterminedamount of movement of said driven member from an initial position.

4. An interlocking mechanism comprising in combination, an operatingmember, a driven member having a rectilinear movement, a yieldabledriving connection between said members, a movable member havingblocking and non-blocking positions with respect to said driven member,and interference means for limiting to a predetermined value the forcetransmitted through said driving connection to said driven membercomprising means interposed to block said operating member at the end ofa predetermined amount of movement from an initial position andremovable from blocking engagement therewith in response to apredetermined amount of said rectilinear movement of said driven memberfrom an initial position.

5. An interlocking mechanism comprising an operating member, a drivenmember, a yieldable driving connection between said members, a movablemember having blocking and non-blocking positions with respect to themovement of said driven member, and interference means comprising ablocking member, means for mounting said blocking member in a positionto block said operating member at the end of a predetermined amount ofmovement from an initial position and means responsive to apredetermined amount of movement of said driven member from an initialposition for removing said blocking member from its blocking position.

6. An interlocking mechanism comprising in combination an operatingmember, a driven member, a yieldable driving connection between saidmembers and interference means for limiting to a predetermined value theforce transmitted from said operating member to said driven membercomprising a member carried by said driven member and positioned toblock said operating member in the event of non-movement of said drivenmember in response to a predetermined amount of movement of saidoperating member.

7. An interlocking mechanism comprising an operating member having aninitial position, a driven member having an initial position, ayieldable driving connection between said members, a movable memberhaving blocking and unblocking positions with respect to the movement ofsaid driven member and interference means for blocking said operatingmember after a predetermined amount of movement from its initialposition thereby to limit to a predetermined value the force transmittedby said driven member to said movable member in its blocking position,and means responsive to a predetermined amount of movement of saiddriven member from its said initial position for moving saidinterference means out of blocking relationship with respect to saidoperating member.

8. An interlocking mechanism comprising in combination an elongatedrod-like driven member having an initial position, means mounting saidmember for lengthwise rectilinear movement, operating means comprising arotatably mounted shaft and an arm mounted on said shaft for rotationtherewith and having an initial position, a first portion of said armhaving an initial movement generally in the direction of said lengthwisemovement and a second portion of said arm having an initial movement ina direction generally perpendicular to the direction of said lengthwisemovement, a yieldable driving connection between said first portion andsaid driven member, means for limiting to a predetermined value theforce transmitted through said driving connection to said driven membercomprising a bracket member mounted on said driven member in position toblock said second portion of said arm in the event of less than apredetermined amount of movement of said driven member from its saidinitial position in response to a predetermined amount of movement ofsaid arm from its said initial position.

9. An interlocking mechanism comprising in combination an elongatedrod-like driven member having an initial position, means mounting saidmember for lengthwise rectilinear movement, operating means comprising arotatably mounted shaft and an arm mounted on said shaft for rotationtherewith and having an initial position, a first portion of said armhaving an initial movement generally in the direction of said lengthwisemovement and a second portion of said am having an initial movement in adirection generally perpendicular to the direction of said lengthwisemovement, a bracket member mounted on said driven member in the path ofmovement of said second portion of said driving member when said drivenmember is in its said initial position, a yieldable driving connectionbetween said first portion of said driving member and said bracketmember for transmitting to said driven member a driving force in thedirection of its rectilinear movement, said bracket member acting toblock said driving member in the event of less than a predeterminedamount of movement of said driven member from its said initial positionin response to a predetermined amount of movement of said driving memberfrom its said initial position.

10. An interlocking mechanism comprising in combination an elongatedrod-like driven member having an initial position, means mounting saidmember for lengthwise rectilinear movement, a rotatably mounted shaft, adriving arm mounted on said shaft for rotation therewith having aninitial position, a first projection on said arm having an initialmovement generally in the direction of said rectilinear movement, asecond projection on said driving arm having an initial movement in adirection generally perpendicular to the direction of said lengthwisemovement, a bracket member mounted on said driven member in the path ofsaid initial movement of said second projection when said driven memberis in its said initial position, a yieldable driving connectioncomprising a spring connected between said first projection and saidbracket for transmitting to said driven member a force to drive it inthe direction of said rectilinear movement to move said bracket out ofthe path of said second projection, said bracket acting to block saiddriving member in the event of less than a predetermined amount ofmovement of said driven member from its said initial position.

11. In combination a first switch having a movable contact-carryingmember, a second switch having a movable contact-carrying member andinterlocking mechanism for said switches comprising a driving memberoperatively connected with the movable contact-carrying member of saidfirst switch, a driven member, a yieldable driving connection betweensaid driving and driven members, an interfering member operativelyconnected with the movable contact-carrying member of said second switchhaving blocking and non-blocking positions with respect to the movementof said driven member, and interference means responsive to relativemovement of said driving member and said driven member for limiting to apredetermined value the force transmitted by said driven member fromsaid driving member to said interfering member.

12. In combination a first switch having a movable contact-carryingmember, a second switch having a movable contact-carrying member andinterlocking mechanism for said switches comprising a driving memberoperatively connected with the movable contact-carrying member of saidfirst switch, a driven member, a yieldable driving connection betweensaid driving and driven members, an interfering member operativelyconnected with the movable contact-carrying member of said second switchhaving blocking and non-blocking positions with respect to the movementof said driven member and interference means comprising a projection onsaid driving member having an initial movement in a direction angularlydisposed with respect to the direction of movement of said driven memberand a blocking member disposed in the path of said initial movement andremovable from said path in response to movement of said driven member.

13. in combination a first switch having a movable contact-carryingmember, a second switch having a movable contact-carrying member andinterlocking mechanism for said switches comprising a driving memberoperatively connected with the movable contact-carrying member of saidfirst switch, a driven member, a yieldable driving connection betweensaid driving and driven members, an interfering member operativelyconnected with the movable contact-carrying member of said second switchhaving blocking and non-blocking positions with respect to the movementof said driven member, and interference means for limiting to apredetermined value the force transmitted by said driven member to saidinterfering member comprising a blocking member, means for mounting saidblocking member in a position to block said driving member at the end ofa predetermined amount of movement of said driven member from an initialposition and means responsive to a predetermined amount of movement ofsaid driven member from an initial position for removing said blockingmember from its blocking position.

14. In combination a first switch having a movable contact-carryingmember, a second switch having a movable contact-carrying member andinterlocking mechanism for said switches comprising an operating member,driving connections between said operating member and the movable memberof said first switch providing a predetermined amount of movement ofsaid operating memher from an initial position while maintaining saidcontact-carrying member of said first switch in switch-closed position,a driven member, a yieldable driving connection between said operatingmember and said driven member, an interfering member operativelyconnected with the movable contact-carrying member of said second switchhaving blocking and non-blocking positions with respect to said drivenmember, and interference means for limiting to a predetermined value theforce transmitted from said operating member to said interfering membercomprising a member carried by said driven member and positioned toblock said operating member in the event of non-movement of said drivenmember in response to said predetermined amount of movement of saidoperating member from said initial position.

15. In combination a first switch having a movable contact-carryingmember a second switch having a movable contact-carrying member andinterlocking mechanism for said switches comprising an elongatedrod-like driven member having an initial position, means mounting saiddriven member for lengthwise rectilinear movement, operating meanscomprising a rotatably mounted shaft and an arm mounted on said shaftfor rotation therewith and having an initial position, drivingconnections between said shaft and the movable member of said firstswitch providing a predetermined amount of rotation of said shaft andsaid arm from an initial position while maintaining saidcontact-carrying member in the switch-closed position, a first portionof said arm having an initial movement generally in the direction ofsaid lengthwise movement and a second portion of said arm having aninitial movement in a direction generally per pendicular to thedirection of said lengthwise movement, a yieldable driving connectionbetween said first portion and said driven member, an interfering memberoperatively connected with the movable contact-carrying member of saidsecond switch having blocking and non-blocking positions with respect tosaid driven member and interference means for limiting to apredetermined value the force transmitted from said operating means tosaid interfering member comprising a bracket member mounted on saiddriven member in position to block the movement of said second portionof said arm in the event of less than a predetermined amount of movementof said driven member from its said initial position in response to saidpredetermined amount of rotation of said arm from its said initialposition.

16. An interlocking mechanism comprising an operating member having aninitial position, a driven member having an initial position, a movablemember having blocking and non-blocking positions with respect to themovement of said driven member, an arm mounted on said operating memberfor movement therewith, a yieldable driving connection between said armand said driven member, means for blocking said operating member after apredetermined amount of movement from its said initial position therebyto limit to a predetermined relatively low value the force transmittedby said driven memher to said movable member in its blocking positioncomprising an interference member pivotally mounted in blockingrelationship in the path of said arm, and means responsive to apredetermined amount of movement of said driven member from its saidinitial position for rotating said interference member out of blockingrelationship with respect to said arm.

17. An interlocking mechanism comprising an operating shaft having aninitial position, a driven member having an initial position andprovided with a bracket having a slot, a movable member having blockingand nonblocking positions with respect to the movement of said drivenmember, a first arm fixedly mounted on said shaft for rotation therewithand provided with a pin, a second arm loosely mounted on said shaft andprovided with a pin engaging said slot, a yieldable driving connectionbetween said pins, means for blocking said operating member after apredetermined amount of movement from its said initial position therebyto limit to a predetermined relatively low value the force transmittedthrough said driven member from said operating member to said movablemember in its blocking position comprising a reaction block pivotallymounted in blocking relationship in the path of said first arm, and aprojection carried by said driven member for rotating said reactionblock out of blocking relationship with respect to said first arm inresponse to a predetermined amount of movement of said driven memberfrom its said initial position.

References Cited in the file of this patent UNiTED STATES PATENTS1,514,378 Fisher et al. Nov. 4, 1924 2,303,49 Peterson et al. Dec. l,1942 2,335,042 Burgess Nov. 23, 1943 2,358,146 Clute Sept. 12, 19442,381,243 Armstrong Aug. 7, 1945 2,444,240 Bayer June 29, 1948

